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14 pages, 6173 KiB

Open AccessArticle

Spurious-Free Shear Horizontal Wave Resonators Based on 36Y-Cut LiNbO₃ Thin Film

by Yushuai Liu, Kangfu Liu, Jiawei Li, Yang Li and Tao Wu

Micromachines 2024, 15(4), 477; https://doi.org/10.3390/mi15040477 - 30 Mar 2024

Cited by 1 | Viewed by 3108

This article presents lithium niobate (LiNbO₃) based on shear horizontal (SH0) resonators, utilizing a suspended structure, for radio frequency (RF) applications. It demonstrates the design, analysis, and fabrication of SH0 resonators based on a 36Y-cut LiNbO₃ thin film. The spurious-free [...] Read more.

This article presents lithium niobate (LiNbO₃) based on shear horizontal (SH0) resonators, utilizing a suspended structure, for radio frequency (RF) applications. It demonstrates the design, analysis, and fabrication of SH0 resonators based on a 36Y-cut LiNbO₃ thin film. The spurious-free SH0 resonator achieves an electromechanical coupling coefficient (

k_{t}^{2}

) of 42.67% and a quality factor (Q_r) of 254 at the wave-propagating orientation of 0° in the 36Y-cut plane. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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15 pages, 5380 KiB

Open AccessArticle

Miniature Ultrasonic Spatial Localization Module in the Lightweight Interactive

by Lieguang Li, Xueying Xiu, Haochen Lyu, Haolin Yang, Ahmad Safari and Songsong Zhang

Micromachines 2024, 15(1), 71; https://doi.org/10.3390/mi15010071 - 29 Dec 2023

Cited by 1 | Viewed by 1167

Abstract

The advancement of spatial interaction technology has greatly enriched the domain of consumer electronics. Traditional solutions based on optical technologies suffers high power consumption and significant costs, making them less ideal in lightweight implementations. In contrast, ultrasonic solutions stand out due to their [...] Read more.

The advancement of spatial interaction technology has greatly enriched the domain of consumer electronics. Traditional solutions based on optical technologies suffers high power consumption and significant costs, making them less ideal in lightweight implementations. In contrast, ultrasonic solutions stand out due to their lower power consumption and cost-effectiveness, capturing widespread attention and interest. This paper addresses the challenges associated with the application of ultrasound sensors in spatial localization. Traditional ultrasound systems are hindered by blind spots, large physical dimensions, and constrained measurement ranges, limiting their practical applicability. To overcome these limitations, this paper proposes a miniature ultrasonic spatial localization module employing piezoelectric micromechanical ultrasonic transducers (PMUTs). The module is comprised of three devices each with dimension of 1.2 mm × 1.2 mm × 0.5 mm, operating at a frequency of around 180 kHz. This configuration facilitates a comprehensive distance detection range of 0–800 mm within 80° directivity, devoid of blind spot. The error rate and failure range of measurement as well as their relationship with the SNR (signal-to-noise ratio) are also thoroughly investigated. This work heralds a significant enhancement in hand spatial localization capabilities, propelling advancements in acoustic sensor applications of the meta-universe. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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15 pages, 5747 KiB

Open AccessCommunication

A High-Sensitivity MEMS Accelerometer Using a Sc_0.8Al_0.2N-Based Four Beam Structure

by Zhenghu Zhang, Linwei Zhang, Zhipeng Wu, Yunfei Gao and Liang Lou

Micromachines 2023, 14(5), 1069; https://doi.org/10.3390/mi14051069 - 18 May 2023

Cited by 4 | Viewed by 2831

Abstract

In this paper, a high-sensitivity microelectromechanical system (MEMS) piezoelectric accelerometer based on a Scandium-doped Aluminum Nitride (ScAlN) thin film is proposed. The primary structure of this accelerometer is a silicon proof mass fixed by four piezoelectric cantilever beams. In order to enhance the [...] Read more.

In this paper, a high-sensitivity microelectromechanical system (MEMS) piezoelectric accelerometer based on a Scandium-doped Aluminum Nitride (ScAlN) thin film is proposed. The primary structure of this accelerometer is a silicon proof mass fixed by four piezoelectric cantilever beams. In order to enhance the sensitivity of the accelerometer, the Sc_0.2Al_0.8N piezoelectric film is used in the device. The transverse piezoelectric coefficient d₃₁ of the Sc_0.2Al_0.8N piezoelectric film is measured by the cantilever beam method and found to be −4.7661 pC/N, which is approximately two to three times greater than that of a pure AlN film. To further enhance the sensitivity of the accelerometer, the top electrodes are divided into inner and outer electrodes; then, the four piezoelectric cantilever beams can achieve a series connection by these inner and outer electrodes. Subsequently, theoretical and finite element models are established to analyze the effectiveness of the above structure. After fabricating the device, the measurement results demonstrate that the resonant frequency of the device is 7.24 kHz and the operating frequency is 56 Hz to 2360 Hz. At a frequency of 480 Hz, the sensitivity, minimum detectable acceleration, and resolution of the device are 2.448 mV/g, 1 mg, and 1 mg, respectively. The linearity of the accelerometer is good for accelerations less than 2 g. The proposed piezoelectric MEMS accelerometer has demonstrated high sensitivity and linearity, making it suitable for accurately detecting low-frequency vibrations. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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33 pages, 7191 KiB

Open AccessArticle

Development and Research of the Sensitive Element of the MEMS Gyroscope Manufactured Using SOI Technology

by Danil Naumenko, Alexey Tkachenko, Igor Lysenko and Andrey Kovalev

Micromachines 2023, 14(4), 895; https://doi.org/10.3390/mi14040895 - 21 Apr 2023

Cited by 1 | Viewed by 2813

Abstract

In this article, based on the developed methodology, the stages of designing the sensitive element of a microelectromechanical gyroscope with an open-loop structure are considered. This structure is intended for use in control units for mobile objects such as robots, mobile trolleys, etc. [...] Read more.

In this article, based on the developed methodology, the stages of designing the sensitive element of a microelectromechanical gyroscope with an open-loop structure are considered. This structure is intended for use in control units for mobile objects such as robots, mobile trolleys, etc. To quickly obtain a ready-made gyroscope, a specialized integrated circuit (SW6111) was selected, for the use of which the electronic part of the sensitive element of the microelectromechanical gyroscope was developed. The mechanical structure was also taken from a simple design. The simulation of the mathematical model was carried out in the MATLAB/Simulink software environment. The mechanical elements and the entire structure were calculated using finite element modeling with ANSYS MultiPhysics CAD tools. The developed sensitive element of the micromechanical gyroscope was manufactured using bulk micromachining technology−silicon-on-insulator−with a structural layer thickness equal to 50

μ

m. Experimental studies were carried out using a scanning electron microscope and a contact profilometer. Dynamic characteristics were measured using a Polytec MSA-500 microsystem analyzer. The manufactured structure has low topological deviations. Calculations and experiments showed fairly accurate results for the dynamic characteristics, with an error of less than 3% for the first iteration of the design. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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15 pages, 4801 KiB

Open AccessArticle

An Ultrasonic Target Detection System Based on Piezoelectric Micromachined Ultrasonic Transducers

by Mingze Gao, Zhihao Tong, Zhipeng Wu and Liang Lou

Micromachines 2023, 14(3), 683; https://doi.org/10.3390/mi14030683 - 19 Mar 2023

Cited by 1 | Viewed by 2230

Abstract

In this paper, an ultrasonic target detection system based on Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) is proposed, which consists of the PMUTs based ultrasonic sensor and the sensor system. Two pieces of 3 × 3 PMUTs arrays with the resonant frequency of 115 [...] Read more.

In this paper, an ultrasonic target detection system based on Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) is proposed, which consists of the PMUTs based ultrasonic sensor and the sensor system. Two pieces of 3 × 3 PMUTs arrays with the resonant frequency of 115 kHz are used as transmitter and receiver of the PMUTs-based ultrasonic sensor. Then, the sensor system can calculate the target’s position through the signal received by the above receiver. The static and dynamic performance of the proposed prototype system are characterized on black, white, and transparent targets. The experiment results demonstrated that the proposed system can detect targets of different colors, transparencies, and motion states. In the static experiments, the static location errors of the proposed system in the range of 200 mm to 320 mm are 0.51 mm, 0.50 mm and 0.53 mm, whereas the errors of a commercial laser sensor are 2.89 mm, 0.62 mm, and N\A. In the dynamic experiments, the experimental materials are the targets with thicknesses of 1 mm, 1.5 mm, 2 mm and 2.5 mm, respectively. The proposed system can detect the above targets with a maximum detection error of 4.00%. Meanwhile, the minimum resolution of the proposed system is about 0.5 mm. Finally, in the comprehensive experiments, the proposed system successfully guides a robotic manipulator to realize the detecting, grasping, and moving of a transparent target with 1 mm. This ultrasonic target detection system has demonstrated a cost-effective method to detect targets, especially transparent targets, which can be widely used in the detection and transfer of glass substrates in automated production lines. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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14 pages, 3028 KiB

Open AccessCommunication

A High Sensitivity AlN-Based MEMS Hydrophone for Pipeline Leak Monitoring

by Baoyu Zhi, Zhipeng Wu, Caihui Chen, Minkan Chen, Xiaoxia Ding and Liang Lou

Micromachines 2023, 14(3), 654; https://doi.org/10.3390/mi14030654 - 14 Mar 2023

Cited by 4 | Viewed by 2874

Abstract

In this work, a miniaturized, low-cost, low-power and high-sensitivity AlN-based micro-electro-mechanical system (MEMS) hydrophone is proposed for monitoring water pipeline leaks. The proposed MEMS Hydrophone consists of a piezoelectric micromachined ultrasonic transducer (PMUT) array, an acoustic matching layer and a pre-amplifier amplifier circuit. [...] Read more.

In this work, a miniaturized, low-cost, low-power and high-sensitivity AlN-based micro-electro-mechanical system (MEMS) hydrophone is proposed for monitoring water pipeline leaks. The proposed MEMS Hydrophone consists of a piezoelectric micromachined ultrasonic transducer (PMUT) array, an acoustic matching layer and a pre-amplifier amplifier circuit. The array has 4 (2 × 2) PMUT elements with a first-order resonant frequency of 41.58 kHz. Due to impedance matching of the acoustic matching layer and the 40 dB gain of the pre-amplifier amplifier circuit, the packaged MEMS Hydrophone has a high sound pressure sensitivity of −170 ± 2 dB (re: 1 V/μPa). The performance with respect to detecting pipeline leaks and locating leak points is demonstrated on a 31 m stainless leaking pipeline platform. The standard deviation (STD) of the hydroacoustic signal and Monitoring Index Efficiency (MIE) are extracted as features of the pipeline leak. A random forest model is trained for accurately classifying the leak and no-leak cases using the above features, and the accuracy of the model is about 97.69%. The cross-correlation method is used to locate the leak point, and the localization relative error is about 10.84% for a small leak of 12 L/min. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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10 pages, 4419 KiB

Open AccessArticle

The Effect of Defect Charge and Parasitic Surface Conductance on Aluminum Nitride RF Filter Circuit Loss

by Tian Xu, Yali Zou, Xuan Huang, Junmin Wu, Shihao Wu, Yuhao Liu, Xuankai Xu and Fengyu Liu

Micromachines 2023, 14(3), 583; https://doi.org/10.3390/mi14030583 - 28 Feb 2023

Cited by 1 | Viewed by 2037

Abstract

When AlN thin films are deposited directly on the high-resistance silicon (HR-Si) substrate, a conductive layer will be formed on the HR-Si surface. This phenomenon is called the parasitic surface conduction (PSC) effect. The presence of the PSC effect will increase the power [...] Read more.

When AlN thin films are deposited directly on the high-resistance silicon (HR-Si) substrate, a conductive layer will be formed on the HR-Si surface. This phenomenon is called the parasitic surface conduction (PSC) effect. The presence of the PSC effect will increase the power consumption of electronic components. Therefore, it is necessary to reduce the PSC effect. In prior technology, the polysilicon layer is usually used as the trap-rich layer to reduce the PSC effect. Experiments show that compared to AlN films deposited directly on HR-Si, the AlN substrates with polysilicon introduced on HR-Si have less radio frequency (RF) loss. To verify the effect of polysilicon on RF loss, polysilicon films of three different thicknesses and several different roughnesses were introduced. The results show that the thickness of the polysilicon will affect the RF loss, while the roughness has almost no effect on it. The polysilicon trap-rich layer can reduce the RF loss, which gradually becomes smaller as the polysilicon thickness increases. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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15 pages, 16533 KiB

Open AccessArticle

Aluminum Nitride Piezoelectric Micromachined Ultrasound Transducer Arrays for Non-Invasive Monitoring of Radial Artery Stiffness

by Sheng Wu, Kangfu Liu, Wenjing Wang, Wei Li, Tao Wu, Heng Yang and Xinxin Li

Micromachines 2023, 14(3), 539; https://doi.org/10.3390/mi14030539 - 25 Feb 2023

Cited by 4 | Viewed by 5388

Abstract

An aluminum nitride (AlN) piezoelectric micromachined ultrasound transducer (PMUT) array was proposed and fabricated for non-invasive radial artery stiffness monitoring, which could be employed in human vascular health monitoring applications. Using surface micromachining techniques, four hexagonal PMUT arrays were fabricated within a chip [...] Read more.

An aluminum nitride (AlN) piezoelectric micromachined ultrasound transducer (PMUT) array was proposed and fabricated for non-invasive radial artery stiffness monitoring, which could be employed in human vascular health monitoring applications. Using surface micromachining techniques, four hexagonal PMUT arrays were fabricated within a chip area of 3 × 3 mm². The mechanical displacement sensitivity and quality factor of a single PMUT were tested and found to be 24.47 nm/V at 5.94 MHz and 278 (in air), respectively. Underwater pulse-echo tests for the array demonstrated a −3 dB bandwidth of 0.76 MHz at 3.75 MHz and distance detection limit of approximately 25 mm. Using the PMUT array as an ultrasonic probe, the depth and diameter changes over cardiac cycles of the radial artery were measured to be approximately 3.8 mm and 0.23 mm, respectively. Combined with blood pressure calibration, the biomechanical parameters of the radial artery vessel were extracted using a one-dimensional vascular model. The cross-sectional distensibility, compliance, and stiffness index were determined to be 4.03 × 10⁻³/mmHg, 1.87 × 10⁻² mm²/mmHg, and 5.25, respectively, consistent with the newest medical research. The continuous beat-to-beat blood pressure was also estimated using this model. This work demonstrated the potential of miniaturized PMUT devices for human vascular medical ultrasound applications. Full article

(This article belongs to the Special Issue Design, Fabrication and Testing of MEMS/NEMS, 2nd Edition)

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